21379855 has 16 divisors (see below), whose sum is σ = 29551104. Its totient is φ = 14545440.

The previous prime is 21379837. The next prime is 21379879. The reversal of 21379855 is 55897312.

It is not a de Polignac number, because 21379855 - 2⁵ = 21379823 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2254 + ... + 6916.

It is an arithmetic number, because the mean of its divisors is an integer number (1846944).

Almost surely, 2^21379855 is an apocalyptic number.

21379855 is a deficient number, since it is larger than the sum of its proper divisors (8171249).

21379855 is a wasteful number, since it uses less digits than its factorization.

21379855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4806.

The product of its digits is 75600, while the sum is 40.

The square root of 21379855 is about 4623.8355290819. The cubic root of 21379855 is about 277.5459653859.

The spelling of 21379855 in words is "twenty-one million, three hundred seventy-nine thousand, eight hundred fifty-five".